The present invention relates to the belt roller of a belt sanding machine, and more particularly to a belt roller adjustment device capable of tightening or releasing rapidly the sanding belt and of adjusting the tightness of sanding belt with precision.
As shown in FIG. 1, the belt roller adjustment device of a conventional belt sander of prior art comprises a driving roller 11 and a driven roller 12, which are disposed respectively at the ends of machine seat 10 of the belt sander 1. A sanding belt 13 is fitted on the outer edges of these two rollers 11 and 12. The main shaft 14 of the driven roller 12 is provided at both ends thereof with support rods 15, each of which has a threaded end arranged on the two support rod seats 16 disposed correspondingly on the machine seat 10. Each of the threaded support rods 15 is provided with a nut 18, which can be rotated to adjust the length of the portion of the support rod 15 extending outside the machine seat 10 and to adjust the distance between the driving and the driven rollers 11 and 12 so as to release or tighten the sanding belt 13.
There are two operational defects of a belt sander of prior art as described above, which are further expounded hereinafter.
As described previously, the adjustment to release or to tighten the sanding belt is accomplished by means of rotating the nut of the threaded support rod. Such manual action of rotating the nut takes time and is therefore not practical from the operational point of view.
The adjustments of the two support rods of the driven roller are done separately and can result in an inconsistency with the lengths of portions of these two support rods extending outside the machine seat. As a result, the shaft center of the driven roller and the shaft center of the driving roller are not parallel. Under such circumstance, a potential safety hazard alway exists when the driven roller is actuated by the driving roller to spin at a high speed.